The present invention is directed to a hand-held tool, such as a hammer, chipping hammer or the like,with a driving unit located within a housing for providing the driving force for the tool and producing vibrations, and a handle connected to the housing and being displaceable in the direction of the main vibration axis between two stops.
Hammer drills and/or chipping hammers with a driving unit which produces vibrations are utilized mainly in the construction trades for drilling and similar working operations. The vibrations generated in the tool can be produced electromechanically, that is, with an electromotor, with a mechanical or electropneumatic percussion mechanism, or pneumatically, hydraulically or electromagnetically for driving such hand-held tools. Due to the reaction forces developed, the vibrations are transmitted in known hand-held tools through the handle to the operator. The stress on the operator's joints and muscles in the operation of such tools can, with time, lead to physical injury. Depending on the type and the operating position of such hand-held tools, the operator must exert a large force of varying extent for maintaining the operation of the tool. With the vibrations developed in the tool superimposed on the contact pressure force required, the operator is exposed to considerable fatigue within a short period of time.
To reduce the transmittal of vibrations through the handle to the operator, it has been known to support the handle on the housing in the direction parallel to the main vibration axis so that the handle is displaceable against the force of spring elements. While such spring elements afford a certain dampening effect, up to the present time it has not been possible to prevent effectively the transmission of vibrations through the handle. A significant disadvantage of such spring elements is that they have a specific natural frequency. Accordingly, a resonance phenomena may develop in the case of changed frequency of the driving unit during operation.